Electron-transfer-mediated benzylic substitution

Lund and coworkers [131] pioneered the use of aromatic anion radicals as mediators in a study of the catalytic reduction of bromobenzene by the electrogenerated anion radical of chrysene. Other early investigations involved the catalytic reduction of 1-bromo- and 1-chlorobutane by the anion radicals of trans-stilhene and anthracene [132], of 1-chlorohexane and 6-chloro-l-hexene by the naphthalene anion radical [133], and of 1-chlorooctane by the phenanthrene anion radical [134]. Simonet and coworkers [135] pointed out that a catalytically formed alkyl radical can react with an aromatic anion radical to form an alkylated aromatic hydrocarbon. Additional, comparatively recent work has centered on electron transfer between aromatic anion radicals and l,2-dichloro-l,2-diphenylethane [136], on reductive coupling of tert-butyl bromide with azobenzene, quinoxaline, and anthracene [137], and on the reactions of aromatic anion radicals with substituted benzyl chlorides [138], with... 

Benzyl chloride and its substituted derivatives are electrochemically reduced indirectly through the mediator, l,4-dihydro-4-methoxycarbonyl-l-methylpyridine anion 35, (equation 27). The rates of the electron transfer between the mediators and benzyl halides, measured by cyclic voltammetry, were found to be about 961 80 M 1 s1. The ratedetermining step was proposed to involve a single electron transfer from the mediator to... 

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